Metabolic diseases, associated with abnormal processing of proteins, carbohydrates, and lipids, are the cause of significant morbidity and mortality. The orphan nuclear receptors, retinoic acid receptor-related orphan receptors 1, -2, and -3 (ROR1, ROR2, and ROR3), play important roles in regulating glucose and lipid metabolism, circadian rhythm, and have been implicated in the pathology of several diseases, including osteoporosis, autoimmune diseases, cancer, and obesity. Detailed examination of mice deficient in ROR1 has revealed a significant amount of information regarding its role in regulating metabolic pathways, including lipid metabolism. ROR3 has been extensively evaluated in regards to its essential role in Th17 cell development and association with certain autoimmune diseases. However, little is known about ROR3's role in other cell types or its mechanism of action. We have identified endogenous, functional ligands (7- oxygenated sterols) for ROR3. Additionally, we recently published that the benzenesulfoamide liver X receptor (LXR) agonist T0901317 is also a high affinity synthetic ligand for ROR3. 7-oxygenated sterols (71-hydroxycholesterol, 72- hydroxycholesterol, and 7-ketocholesterol) play important physiological and pathological roles in humans. The long-term objective is to determine the role of these ligands in regulating the activity of ROR3. We hypothesize that 7-oxygenated sterols are key ligands that regulate ROR3 mediated cellular processes. Our hypothesis will be tested in the following specific aims: Specific Aim 1 will determine the specificity of ROR3 for various sterols;Specific Aim 2 will determine the specificity of synthetic ligands on ROR3;and in Specific Aim 3 we will determine the effects of natural and synthetic ligands on ROR3 regulated physiological processes. These studies are essential for our understanding of how ligands may coordinate ROR3 regulated functions. Ligand-regulated nuclear hormone receptors have been definitively shown to be effective targets for the development of pharmaceuticals. We predict that these studies will provide the basis for novel therapeutics targeting ROR3 for the treatment of metabolic disorders. PUBLIC HEALTH RELEVANCE: The orphan nuclear receptors, retinoic acid receptor-related orphan receptors 1, -2, and -3 (ROR1, ROR2, and ROR3), play important roles in regulating glucose and lipid metabolism, circadian rhythm, and have been implicated in the pathology of several diseases, including osteoporosis, autoimmune diseases, cancer, and obesity. We have identified endogenous functional ligands (7-oxygenated sterols) for ROR3 and while ROR3 has been extensively evaluated in regards to its role in Th17 cell development and association with certain autoimmune diseases, little is known about ROR3's role in other cell types or its mechanism of action. Ligand- regulated nuclear hormone receptors have been definitively shown to be effective targets for the development of pharmaceuticals and we predict that our proposed studies may provide the basis for novel therapeutics targeting ROR3 for treatment of metabolic diseases.